Mimi, Have you thought about trying the 0.5 size in the 40? I wear a 38 and my old pair of Sidi's were 38. Then I got a 38.5 in Genius and Dominator shoes and it made a HUGE difference in the toe box width. I have chronic issues with my feet (bunion, arthritis, etc.) and now my Sidi shoes are among the most comfortable of all my shoes.